Flood Plain Regulations

Questions from last Stakeholder Meeting. 1 Questions from last Stakeholder Meeting 1. How do regulations regarding fill prevent serious issues from developing? 2. What are the regulations for placing fill in floodplains and floodways? 3. Does the City or County pay attention to fill in the Floodway? Also Clarify which rules apply to fill within the floodplain and Where within the floodplain do the different rules apply Let’s take the last question first, and to do that, start with a little background information.

Flood Plain Regs vs Clean Water Act Flood Plain Regulations live in the National Flood Insurance Program – NFIP Administered by FEMA through local participating agency Purpose Balance Protection and recovery from flooding with Preserving private property rights Clean Water Act Regulations live in the Clean Water Act Administered by EPA through Corps of Engineers and state DNR Ensure Waters of the State are Clean No Explicit Connection Between the 2 Regulations

Flood Plain Cross Section Schematic

Fill Allowed Where, Who Governs? Fill Allowed in Floodway Fringe Permit Required From Local Floodplain Administrator Fill Prohibited in Floodway Unless NO-RISE Certified to Local Floodplain Administrator If you want to place something (fill, pipe, etc) within the Ordinary High Water Mark, you need a permit from the Army Corps of Engineers AND a Floodplain Development Permit from whoever administers the NFIP in your jurisdiction. Fill Within Ordinary High Water Permit Required from Corps of Engineers Fill Prohibited unless “No-Rise” Certified

Back to the first 3 Questions Fill in the Floodplain and Floodway are handled through the NFIP Basic components to NFIP 1. Mapping – producing the maps to aid regulation and insurance 2. Regulations – stipulating what one can and can’t do in a flood plain 3. Insurance – providing flood insurance for folks Plus, promoting mitigation, which involves doing things to prevent flooding and preventing losses due to flooding.

Mapping 3 Primary Tasks Estimating Flood Flows Modeling the flows through topo of floodplain Mapping the results

Modeling Flows in Floodplain First the Base Flood Elevations are Established BFE = 100-year flood = 1% flood 1% chance of happening in a given year a 100yr flood has 26% chance of happening during a 30-yr mortgage (5% chance of fire occurring)

Then the Floodway is Established Floodway = the idealized (in modeling) encroachment on the floodplain from each side that will cause 1 foot of rise of 100-yr flood

Regulations Two Main Requirements Build Above BFE Columbia Requires 2’ above BFE (FEMA Requires 1” above) Stay out of the Floodway If building in the Floodway is necessary, Certify “NO-Rise” in BFE i.e. Structures like bridges need “no-rise”

Floodway Purpose a way of keeping everyone on same page Existing House Built on premise that no one downstream can build in a way that causes more than 1 foot of rise in BFE. Floodway Flood Plain Proposed House Must stay out of floodway to ensure the premise for existing houses stays true

Development in Flood Plain Per City Rules: Low Floor Must be at least 2 feet above BFE. Functionally difficult/expensive to fill to the floodway boundary No Fill Allowed in Floodway Without “No-Rise” Certificate

Questions from last Stakeholder Meeting 1 Questions from last Stakeholder Meeting 1. How do regulations regarding fill prevent serious issues from developing? A. Make sure folks build high enough B. Make sure there is no more than 1 foot of rise in BFE by keeping folks out of floodway 2. What are the regulations for placing fill in floodplains and floodways? A. Fill in Flood Plain is Allowed B. Fill in Floodway NOT Allowed 3. Does the City or County pay attention to fill in the Floodway? Absolutely! In order to participate in the NFIP, the City and the County agree to enact and enforce regulations to keep this from happening. Let’s take the last question first, and to do that, start with a little background information.

Questions?

Estimating Flows Best available information Stream gauge on creek being modeled Gauge on Hinkson near Providence is spotty but valuable Stream guages from other, similar creeks Other information Soils and ground cover information Rain gauge data Caution! 100-year storm does not produce 100-year flood